Patent document 1 discloses a filler pipe mounting structure with a filler pipe mounted on a resin fuel tank. FIG. 5 is a cross sectional view showing a conventional filler pipe mounting structure. The filler pipe mounting structure 100 is mainly composed of: a mounting member 102 fixed to a sidewall of a fuel tank 101; and a filler tube 103 fitted over an end of the mounting member 102. The filler tube 103 is a component of a filler pipe located at the end thereof on the side of the fuel tank 101.
The mounting member 102 includes: a flange 102a that covers an opening 101a formed in the sidewall of the fuel tank 101; and a filler-tube connecting section 102b that is cylindrically shaped and extends upright from the flange 102a. The flange 102a is welded to the outer surface of the sidewall of the fuel tank 101 around the peripheral edge of the opening 101a. The sidewall of the fuel tank 101 is made up of resin layers X, X and a barrier layer Y interposed between the resin layers X, X.